1. Field of the Invention
The present invention is generally related to exhaust cooling systems for marine engines and, more particularly, to an exhaust cooling system for marine propulsion units in which water flow through exhaust manifolds is controlled by a microprocessor that receives information regarding the temperature of the water within the manifolds and then controls the flow into the manifold as a function of that measured temperature.
2. Description of the Related Art
Exhaust systems for marine propulsion devices have used water, typically drawn from a body of water, as the cooling medium to regulate the temperature of the exhaust components.
U.S. Pat. No. 3,734,170, which issued to Pace on May 22, 1973, describes a marine engine cooling system. Improved water jacketed manifolds for marine engine cooling systems of the type wherein heated water which is circulated through an engine cooling system for cooling purposes is mixed in the improved engine exhaust manifold water jacket is described. The heated water is mixed with raw, relatively cool water to controllably cool the manifold and avoid condensing water from the exhaust gases flowing through the exhaust manifold.
U.S. Pat. No. 3,780,712, which issued to Pace on Dec. 25, 1973, describes a marine engine cooling system. This patent is a division of U.S. Pat. No. 3,734,170.
U.S. Pat. No. 4,573,318, which issued to Entringer et al. on Mar. 4, 1986, discloses an exhaust elbow for a marine propulsion system. The elbow has an intake exhaust passage extending upwardly from the engine and communicating through a bend with a discharge exhaust passage, and a water jacket has pockets around the exhaust passages for cooling the latter. A central channel extends longitudinally along the exterior of the exhaust passages to guide water to the end of the discharge exhaust passage to mix with exhaust. The central channel has a pair of side walls extending longitudinally and laterally tapered away from each other at the outer end of the discharge exhaust passage to create an outward draw from the central channel to minimize breakup of longitudinally outward water flow and maintain the end tip of the discharge exhaust passage dry and prevent water ingestion and creeping back into the discharge exhaust passage due to pulsations of the engine.
U.S. Pat. No. 4,866,934, which issued to Lindstedt on Sep. 19, 1989, discloses a marine drive exhaust system with shaped O-ring seals. The system is provided with resilient, shaped rubber O-ring seals between facing surfaces of the exhaust manifold and exhaust elbow and the facing surfaces of the exhaust elbow and the exhaust pipe. Each of the shaped O-ring seals has an inner peripheral rib extending peripherally around the exhaust passage and generally conforming to the shape thereof. They are spaced laterally between the exhaust passage and the peripheral water passages.
U.S. Pat. No. 4,977,741, which issued to Lulloff et al. on Dec. 18, 1990, discloses a combination exhaust manifold and exhaust elbow for a marine propulsion system. It includes an exhaust cavity for receiving exhaust from the engine, an exhaust passage leading from the exhaust cavity, and an exhaust discharge outlet. A first water jacket is provided around the exhaust cavity and a second water jacket is provided around the exhaust discharge passage. A dam is provided between the first and second water jackets, having a passage therein for allowing fluid communication between the first and second water jackets.
U.S. Pat. No. 4,991,546, which issued to Yoshimura on Feb. 12, 1991, describes a cooling device for a boat engine. An engine cooling jacket delivers its coolant to an exhaust manifold cooling jacket adjacent the inlet of the exhaust manifold and coolant is delivered from the exhaust manifold cooling jacket to a further cooling jacket around the inlet portion of an exhaust elbow.
U.S. Pat. No. 5,032,095, which issued to Ferguson et al. on Jul. 16, 1991, describes a marine engine with galvanic circuit protection. An engine includes a cooling jacket and an exhaust port, an exhaust gas discharge system includes an exhaust gas manifold communicating with the exhaust port, and a high rise elbow communicates with the exhaust gas manifold. An exhaust pipe communicates with the high rise elbow and is adapted to convey exhaust gas to an overboard discharge. A high rise elbow and exhaust gas manifold cooling jacket surrounds the exhaust gas manifold and at least partially surrounds the high rise elbow and communicates with the exhaust pipe for discharge of coolant from the high rise elbow and exhaust gas manifold cooling jacket.
U.S. Pat. No. 5,109,668, which issued to Lindstedt on May 5, 1992, discloses a marine exhaust manifold and elbow. The exhaust assembly includes a manifold portion, an elbow portion, a water jacket portion, and exhaust runner walls. It provides a smooth continuous transition of exhaust gas flow from the intake exhaust passages in the manifold portion to transfer exhaust passages in the elbow portion around a bend to a discharge exhaust passage. This minimizes turbulent flow of exhaust through the manifold portion and elbow portion.
U.S. Pat. No. 6,652,337, which issued to Logan et al. on Nov. 25, 2003, discloses an exhaust system for a marine propulsion engine. The system provides a relationship between the exhaust passages and coolant passages of the exhaust manifold and exhaust elbow which serves to maintain the joint of the exhaust passage at a higher temperature than would be possible with known exhaust manifolds and exhaust elbows. By providing a space between the surfaces of a raised exhaust portion of the components and surfaces of the raised coolant portions of the exhaust system, leakage from the coolant conduits of the exhaust cavities is avoided.
U.S. Pat. No. 6,672,919, which issued to Beson on Jan. 6, 2004, describes a temperature control system for a marine exhaust system. The control system lowers flow of cooling water to water jacket and exhaust gas conduit portions of the exhaust system at low engine speeds. The control system is typically activated at and below a predetermined engine speed. Once activated the control system operates to reduce flow of cooling water to the exhaust system.
U.S. Pat. No. 6,929,520, which issued to Hughes et al. on Aug. 16, 2005, discloses a cooling method for a marine propulsion system. The method directs a portion of a recirculating stream of cooling water to a first portion of an exhaust manifold so that a cooling jacket of the exhaust manifold can be maintained in a filled condition. Water flows upwardly through the cooling jacket and exits through a port in the exhaust manifold back into the recirculating stream of cooling water that passes through a recirculation pump, the cooling passage of an engine, and a cavity of a thermostat housing.
U.S. Pat. No. 7,065,961, which issued to Batten on Jun. 27, 2006, discloses an exhaust system with an integral moisture trap. The trap is formed as an integral part of the wall of an exhaust conduit. Tapered surfaces can be provided to direct condensate downwardly and into a reservoir of the moisture trap where the moisture is retained until the temperature of the exhaust system reaches adequate magnitude to evaporate the water and conduct it out of the exhaust system along with exhaust gases.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
When exhaust components are cooled with water drawn from a body of water, it presents several difficulties that must be addressed. First, when the exhaust system components have not reached their maximum or near maximum temperatures, provision of cold water can cause condensation within those exhaust components. The condensation can lead to several disadvantageous conditions that are well known to those skilled in the art. On the other hand, if adequate cooling water is not provided when the engine is operating at its maximum or near maximum heat production levels, exhaust system components can quickly overheat and be damaged. It is therefore significantly beneficial if a system can be provided to control the flow of water to the exhaust system components, such as exhaust manifolds and exhaust elbows, in a manner that neither overcools nor overheats those components.